1. Field of the Invention
The present invention relates generally to wireless communications devices and technologies, and more particularly pertains to a communications protocol for small hand-held wireless devices that effectively minimizes the power consumption of the hand-held wireless devices. More particularly, the present invention relates to a power optimized request response communication protocol which provides a natural protocol that allows a user device to make tradeoffs between power consumption and other scarce and expensive resources and functions (e.g. bandwidth, transmission range, latency, etc.).
2. Discussion of the Prior Art
Today's communications protocols were generally not designed specifically to support small, limited power, wireless, mobile devices. In particular, they do not give the user effective control over power consumption.
Existing communications protocols for mobile client devices, such as pagers, use synchronized time slots to wait for unsolicited messages from a server. In such protocols, the client goes into a low power mode from which it is periodically woken up to listen for server messages. This monitoring process often consumes power continuously, because it is implemented at the network level with no convenient user or application control to permit intelligent tradeoffs between power consumption and frequency of polling.
The following is a brief description of the main activities in prior art wireless communications along with their advantages and disadvantages with respect to power consumption.
The IEEE 802.11 committee has defined a standard for Wireless LAN [IEEE 802.11, “Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications”, November 1997]. The standard supports both ad-hoc networking, in which peer nodes communicate directly, and infrastructure networking, in which nodes called access points (AP) are interconnected over a distribution system. Wireless LAN implementations require continuous connection to the network and are, therefore, inefficient in power utilization. Although power conservation modes exist, even advanced implementations can only work up to 12 hours using of the shelf battery before recharging is needed. Another disadvantage is that Wireless LAN (WLAN), devices are very expensive and large in size, hence are not suitable for small hand-held devices.
Bluetooth is a standard for low-cost, low-power, radio frequency connectivity for various devices, such as PDAs, cellular phones, and other cost-sensitive information appliances [J. C. Haartsen, “The Bluetooth Radio Sytem”, IEEE Personal Comm., February 2000, pp. 28–36]. Bluetooth was originally designed to enable mobile devices, in proximity with each other, to establish an ad-hoc cell called picocell and exchange information. In summary, the high frequency hopping (FH) rate, the need for synchronization between master and slave, and other design problems limit the ability to achieve really low power consumption using the Bluetooth standard.
Mobile Telephone Systems are widely used all over the world. The penetration of cellular phones into the marketplace has been incredibly fast and continues to grow. MTS is a Wide Area Network (WAN) in nature and it is meant to be able to supply coverage for wide areas with an assumed distance of a few thousand meters between the mobile unit and the base station [W. C. Y Lee, “Mobile Cellular Telecommunications Systems”, McGraw-Hill, N.Y., 1989]. In summary, the need for a circuit switched network for best support of voice, and the need to continuously listen for incoming calls, in addition to the assumption about the distance between the access point and the mobile device, do not allow the proposed power conservation scheme particularly not to totally shut of the client transceiver.